Chemistry · Ch 3 — p-Block Elements-II
Oxides and oxoacids of nitrogen
Oxides and oxoacids of nitrogen
Nitrogen forms a remarkably complete series of oxides spanning every oxidation state from +1 to +5, each with characteristic physical properties and a distinct preparation. Nitrous oxide, N2O (+1), is a colourless, neutral gas obtained by the thermal decomposition of ammonium nitrate (NH4NO3 -> N2O + 2H2O); its resonance structure is best represented as a linear N=N=O with delocalised bonding. Nitric oxide, NO (+2), is a colourless, neutral, paramagnetic gas (it has an unpaired electron) prepared by reducing sodium nitrite with acidified ferrous sulphate (2NaNO2 + 2FeSO4 + 3H2SO4 -> Fe2(SO4)3 + 2NaHSO4 + 2H2O + 2NO). Dinitrogen trioxide, N2O3 (+3), is a blue, acidic solid formed by combining nitric oxide and nitrogen dioxide/tetroxide (2NO + N2O4 -> 2N2O3); structurally it can be viewed as a nitroso group (-N=O) joined by an N-N bond to a nitro group bearing formal + and - charges. Nitrogen dioxide, NO2 (+4), is a brown, acidic, paramagnetic (odd-electron) gas produced by the thermal decomposition of heavy-metal nitrates such as lead nitrate (2Pb(NO3)2 -> 4NO2 + 2PbO + O2); it is in equilibrium with its colourless dimer, nitrogen tetraoxide N2O4 (also +4 oxidation state), the two NO2 units joining through an N-N bond. Nitrogen pentoxide, N2O5 (+5), is a colourless, acidic solid, obtainable by dehydrating nitric acid with phosphorus pentoxide (2HNO3 + P2O5 -> N2O5 + 2HPO3); it consists of two pyramidal nitrate-type NO2 fragments bridged by a central oxygen. …
Nitrous oxide N2O, +1, colourless neutral gas: NH4NO3 -> N2O + 2H2O
Nitric oxide NO, +2, colourless neutral gas: 2NaNO2 + 2FeSO4 + 3H2SO4 -> Fe2(SO4)3 + 2NaHSO4 + 2H2O + 2NO
Dinitrogen trioxide (nitrogen sesquioxide) N2O3, +3, blue acidic solid: 2NO + N2O4 -> 2N2O3
Nitrogen dioxide NO2, +4, brown acidic gas: 2Pb(NO3)2 -> 4NO2 + 2PbO + O2
Nitrogen tetraoxide N2O4, +4, colourless acidic solid: 2NO2 -> N2O4 …
N2O: linear N=N=O (resonance N≡N-O <-> N=N=O). NO: diatomic, N=O bond length 115 pm, one unpaired electron. N2O3: planar, one N bears a positive and the other a negative formal charge, O-N=O on the nitroso nitrogen linked by an N-N bond to the nitro group -N(=O)O-. NO2: bent (V-shaped) with one unpaired electron delocalised over the O-N-O framework. N2O4: planar, formed by N-N coupling of two NO2 units, each nitrogen bearing formal + and - charges from resonance. N2O5: two NO2 groups …
Hyponitrous acid H2N2O2, +1: Ag2N2O2 + 2HCl -> 2AgCl + H2N2O2
Nitrous acid HNO2, +3: Ba(NO2)2 + H2SO4 -> 2HNO2 + BaSO4
Pernitrous acid HOONO, +3: H2O2 + ON-OH -> ON-OOH + H2O
Nitric acid HNO3, +5: 4NH3 + 5O2 -> 4NO + 6H2O; 2NO + O2 -> 2NO2; 2NO2 <-> N2O4; 4HNO3(from N2O4 + H2O + O2 route) …
Hyponitrous acid H2N2O2: HO-N=N-OH (trans). Hydronitrous acid H4N2O4: an unstable tetrahydroxy hydrazine-type N-N species, (HO)2N-N(OH)2. Nitrous acid HNO2: planar H-O-N=O. Pernitrous acid HOONO: H-O-O-N=O (a peroxo N-O-O linkage). Nitric acid HNO3: planar, one N=O and two equivalent N-O(H)/N-O- bonds by resonance, trigonal planar at N. Pernitric acid HNO4: ni …